Research has consistently shown extensive comorbidity between anxiety and depression, but little is known about why this is the case. Substantial research shows anxiety tends to temporally precede depression, a finding with important implications for comorbidity models. Several researchers have suggested that anxiety acts as a risk factor for the development of depression; however, little research has attempted to identify mechanisms through which this may occur. One way that anxiety may elicit later depression is by activating depressogenic processes. First, some individuals may feel hopeless about their anxiety, perhaps sparking depression. Second, some individuals may ruminate about anxiety symptoms, possibly leading to depression. Third, anxiety may provoke interpersonal difficulties, such as low social support, criticism, or rejection, also possibly leading to depression. As comorbidity is especially prevalent at the symptom level, examining comorbid symptoms (e.g., depressed and anxious mood) may provide insight into comorbidity mechanisms. I propose to examine several hypotheses using a diary design. First, I predict that daily anxious mood will predict later depressed mood (as has been shown in longitudinal designs). [unreadable] [unreadable] Second, I predict that symptom-focused hopelessness, rumination, and interpersonal factors will mediate the relationship between anxious mood and later depressed mood. I also plan to examine a further question. Women are more vulnerable to both depression and anxiety. While research has mainly focused on sex differences in depression, some evidence suggests that depression sex differences are partially accounted for by sex differences in anxiety. If this is the case, it is doubly important to understand sex differences in anxiety. One logical starting point is to determine whether existing theories of depression sex differences also apply to anxiety. I will test the applicability of one such theory, the Response Styles Theory, by examining whether rumination accounts for gender differences in anxiety. I will examine these questions in 2samples: 1) highly stressed law students (n=250); 2) individuals with comorbid GAD/depression (n=40). [unreadable] [unreadable] [unreadable]